Evangeline, a young Franciscan nun, works in the library of the Convent of Sainte-Rose, famous for its collection of images of angels. One day, a girl discovers a letter from the famous philanthropist Abigail Rockefeller, addressed to the former abbess. The letter talks about some kind of expedition sent to Bulgaria in 1943. It seems that there, in the Rhodope Mountains, something extremely important was discovered. Thus begins the solution to a great mystery that goes back thousands of years into the past, to the beginning of the endless war of the human race with beautiful monsters - the Nephilim, the descendants of those whom the “daughters of men” gave birth to “ sons of God."